This document summarizes research on the cognitive neuroscience of empathy. It discusses how mirror neurons in the brain allow people to naturally understand and share the feelings of others (emotional contagion). Experiments show that when people observe facial expressions of emotions, the same areas of their brain are activated as if experiencing that emotion firsthand. The document also notes that people more easily empathize with in-group members due to increased activation of brain regions involved in mentalizing. While empathy has long been recognized as important for human relationships, modern neuroscience now provides biological evidence for how and why humans connect with each other.